The current live attenuated vaccine for tuberculosis, BCG, has variable and limited efficacy in tuberculosis-endemic regions. For a vaccine to be effective it must cause the generation of a strong immune response against M. tuberculosis. Until now researchers in this field have concentrated on CD4 T cell and antibody responses to M. tuberculosis. A correlation has not been shown in humans between infection with M. tuberculosis and the generation of a CD8 T cell response against specific M. tuberculosis antigens.